Horse-riding is well known as an effective exercise for preventing lumbago and for increasing muscular strength of legs and loins. However, it is difficult that most of people living in cities go to horse-riding facilities from viewpoints of time and expense. In addition, there is a danger that an unripe person in horse-riding technique falls from a horseback. Therefore, attention is being given to an apparatus for providing an artificial horse-riding exercise by simulating an exercise that the user receives during the horse-riding.
For example, Japanese Patent Publication [kokoku] No. 6-65350 discloses a balance training apparatus comprising a horse-shaped seat for a user, six independent drive motors, and a power transmission unit for transferring outputs of these motors to the seat. In this apparatus, it is possible to separately control six motions of rectilinear reciprocating motions in a forward and backward direction, left and right direction, and an upward and downward direction, and pivotal reciprocating motions about an axis of the forward and backward direction, axis of the left and right direction, and an axis of the upward and downward direction. In the case of providing these rectilinear reciprocating motions and pivotal reciprocating motions to the user on the seat at required speeds, a position of the center of gravity of the user's body changes during the exercise. Since the user holds out, bracing the legs to keep the head position constant, it is possible to efficiently train specific muscles of the user.
By the way, from a detail analysis of the present inventors about a relation between muscle motions in the horse-riding exercise and an effect of increasing the muscle power brought thereby, it has been concluded that a combination of specific three motions in the above-described six motions is particularly effective for the balance training and the lumbago prevention. That is, it has been revealed that the rectilinear reciprocating motion in the forward and backward direction of the seat and the pivotal reciprocating motion about the axis extending in the horizontal direction substantially perpendicular to the forward and backward direction are effective for abdominal and back muscles, and the pivotal reciprocating motion about the axis extending in the forward and backward direction is effective for external abdominal oblique muscle. In addition, it has been revealed that even when the remaining motions other than the above-described three motions are given to the user, remarkable effects of increasing the muscle power cannot be expected. Thus, from the viewpoint of efficiently training the specific muscles of the user, there is still room for improvement in the conventional balance training apparatus.
In addition, since many motors built in the conventional apparatus bring about an upsizing of the apparatus, the ease-of-use of the apparatus is not often satisfied in average homes and offices. Moreover, the use of a lot of motors and the upsizing of the apparatus lead to poor cost/performance. Consequently, it has become a very expensive apparatus to the average homes.